Strange one this that I've just noticed. My iMac has 4Gb RAM and this morning I had a problem with the blued process chewing up memory even though Bluetooth was off and I don't ever use it. After a bit of searching I found the probable cause. Anyway, whilst looking at the above issue, my system was really crawling but the memory usage wasn't over 70% and CPU usage was low too. The swap space usage had jumped up to 4Gb and all the time I was opening new Safari windows researching the issue. The system was getting more and more sluggish and the swap usage was growing but memory usage stayed at 70%. Why wouldn't it use the last 30%?